Lighting trends in residential and commercial applications are taking advantage of the increased dimming and color control offered by LED light fixtures. However, the efficiency of a fixture is affected by the color and intensity level of the light output. Energy codes are starting to incorporate color tunable products and expectations for efficiency across the tunable range. Thus, there is a need for a lighting product which is efficient across a wide range of intensities and color temperatures.
There is a demand for light sources that produce adjustable white light across a range of correlated color temperatures (CCT or color temperature), such as from about 6000K to about 1800K; products of this type are often called tunable white products. There is also a demand for light sources that provide light with a warm color temperature, such as from about 2700K to about 1800K, especially if the light intensity may be dimmed; products of this type are often called warm dimming products. Additionally, there is a demand for high-efficiency lighting products, to improve energy budgets and to meet energy efficiency standards. However, when using LED light fixtures, warmer color temperatures are historically of lower efficiency, as LEDs of warmer colors require a less efficient phosphor coating to counteract the blue color of the underlying diode, necessitating more and brighter LEDs to reach a given level of illumination. In existing products, a product is typically either a warm dimming product or a tunable white product. It is desirable to have a product with benefits of both without suffering decreased energy efficiency at lower CCTs.